802.16e standard is a broadband wireless access standard established by IEEE standards organization; compared with 802.16 standard, many methods to support the mobile station mobility are added, such as handover and power saving mechanism.
Idle mode is a very important power saving mechanism in 802.16e system. In order to support the paging of mobile station (MS) in Idle mode, the standard offers the concept of paging group. Several base stations (BS) are divided into a paging group, and overlapping is allowed among the paging groups. Several paging groups are managed by a paging controller (PC). As shown in FIG. 1, base station 0 and base station 1 belong to the paging group A, base station 1 and base station 2 belong to the paging group B, and the paging controller 0 and the paging controller 1 control the paging group A, the paging controller 0 and paging controller 1 are connected with Location Register (LR) respectively to store the MS-related information, and the paging controller 0 and the paging controller 1 simultaneously connect with the base station 0 and the base station 1 to originate the paging for the MS in the paging group A. The access network gateway (ASN-GW) simultaneously connects with the paging controller 0 and the paging controller 1.
The structural diagram of the network of 802.16e system is shown as FIG. 2, which includes function modules such as the base station (BS), the relay access network gateway (Relay ASN-GW), the anchor access network gateway (Anchor ASN-GW), the home agent (HA), the authenticator, the relay paging controller (Relay PC) and the anchor paging controller (Anchor PC), and so on.
The base station connects with the Anchor ASN-GW (or through the Relay ASN-GW), who is charge for the egress routing of IP network segment where the whole access network locates, and the Anchor ASN-GW connects with the authenticator which is the authentication logic module in EAP protocol and takes charge of the authentication of the mobile station. For mobile IP, the Anchor ASN-GW implements the function of foreign agent (FA) and connects with the HA through IP network. The data sent to the mobile station is forwarded to the Anchor ASN-GW by the HA through the mobile IP tunnel.
The Anchor paging controller controls the paging of the mobile station and the position renewal, and the storage of the associated information of the MS. The Delay paging controller takes charge of the forwarding of the Paging Announce message between the Anchor paging controller and the base station.
The home agent is a function entity in the mobile IP mechanism, and its responsibility is to maintain the local registration information, the position information of the mobile station and forward the date routed to the mobile station to the foreign agent or the mobile station through the mobile IP channel.
When the MS is in Idle mode and downlink traffic data arrives, the Anchor PC is responsible for originating a paging process, and partial or all BSs in the paging group to which the MS belongs will send the MOB-PAG-ADV (mobile paging advertisement) message, and the MS will decide whether it needs to exit Idle mode and re-access the network according to the indication in the MOB-PAG-ADV message.
When the mobile station is switched from the normal mode to the Idle mode, the current information of the mobile station (including the basic functions and the traffic stream information) should be saved in Anchor PC, and once the MS is aroused in Idle mode, it can retrieve the associated message from the Anchor PC and accelerate the process of network access.
How to shorten the time for the mobile station accessing the network in the process of paging is one of hotspots of the present research. The basic process of paging is offered by the NWG working group in the Wimax organization. However, the deficiency of the process is that after the terminal MS starts the flow of accessing, the BS obtains the Authenticator ID from the response message for the MS Info (mobile station information) Request message of the Anchor PC (the Anchor paging controller), and afterwards, the BS interacts with the authenticator to obtain the key for the HMAC/CMAC authentication of the ranging request (RNG-REQ) message, thus lengthening the time of the paging access of the mobile station.